Receiver-transmitting arrangement



Patented Feb. ll, 1947 v ancarvnn-raausivnrrma ARRANGED/[ENE Harold A. Wheeler", Great Neck, N. Y., 'assignor, -by mesne assignments, to Hazeltine, Research,

Inc., Chicago, 111., a corporation of Elinois Application February 11, 1944, Serial No. 521,931

8 Claims. i

This invention relates,

in general, to receivertransmitter arrangements of the regenerative type tive receiver for the reception of interrogating signals and as a radio-frequency transmitter for the transmission of reply signals. This dual function of the regenerative oscillatory circuit results from the operating potentials which are applied ,to the oscillator tube. In the system under consideration, a, periodic quench voltage is applied to the control electrode-cathode circuit of the tube to provide superregeneration for wave signal reception, while on the other hand, a modulated potential is applied to the control electrodecathode circuit ofthe tube so that the regenerative oscillatory circuit comprises a high-power radio-frequency transmitter for wave-signal transmission.

ing frequency of the regenerative. oscillatory circuit is the same for receiving and transmitting, which is undesirable in installations where the P- erating frequency of the system during signal reception is required to be different from that during transmission.

It is, therefore, an object of the invention to provide an improved regenerative-type receivertransmitter arrangement which avoids one or more of the aforementioned limitations of prior art arrangements.

It is another object of the invention to provide an improved regenerative-type receiver-transmitter arrangement having an improved stability terrogating signal, the reply and interrogating l5 characteristic. g signals preferably comprising radiant-energy It is still another object of the invention to prowave signals. vlde an improved regenerative-type receiver- In certain regenerative-type transpondor systransmitter arrangement for receiving and transtems of the prior art,'the receiving and transmitting modulated carrier-frequency wave signals mitting units are completely discrete and separate and having a predetermined shift in operating I circuit arrangements, but in others the receiving frequency as between intervals of wave-signal and transmitting units have some common cirreception and transmission. cuit elements. One prior art arrangement in In accordance with the invention, a regeneraparticular includes a single regenerative osclllative-type receiver-transmitter arrangement for torycircuit which is utilized as a superregene'rareceiving and transmitting modulated carrierfrequency wave signals comprises a single regen- I erative oscillatory circuit including vacuum-tube means having an anode-cathode circuit. The

arrangement also comprises means for supplying to the anode-cathode circuit a periodic quench voltage to provide superregeneration for wavesignal reception, the quench voltage having a frement includes means for deriving from the re- The described arrangement has the advantage of minimizing the expense and space requirements of the transpondor equipment but it has tors in the control circuit in order to minimize power dissipation. These high-impedance elements have a tendency to develop excessive bias voltage during periods of oscillation, thereby ungenerative oscillatory circuit an output signal representing the modulation of the received signal.

Additionally, the arrangement has means for supplying to the above-mentioned anode-cathode circuit a modulated potential for controlling the regenerative oscillatory circuit to transmit a modulated carrier-frequency signal. The operating frequency of the arrangement is influenced by the magnitude of the potential applied to the anodecathode circuit and, in certain applications of the invention, the quench voltage and modulated potential are selected of such relative. values as to desirably to block the regenerative oscillatory cirthe control electrode-cathode circuit, the operateffect a desired shift in the operating frequency as between intervals of wave-signal reception and transmission. It is also contemplated that means be included, in some embodiments of-the invention, for effectively disabling either the quench vals when the other is to be effective in controlling the regenerative circuit.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

In the drawing, Fig. 1 represents a wave-signal transpondor system in accordance with the invention; Fig. 2, comprises a graph utilized in explaining an operating characteristic of the transpondor system of Fig. 1; while Fig. 3 illustrates a modified form of a portion of the Fig. l arrangement.

Referring nowv more particularly to the drawing, there is represented in Fig. l a regenerativetype receiver-transmitter arrangement, specifically, a wave-signal transponder system for operation in the ultra-high-frequency range and for receiving and transmitting carrier-frequency wave signals. For convenience of explanation, the system may be considered as a radio beacon adapted to transmit direction-finding information to inquiring aircraft. As represented, the

radio beacon comprises a single regenerative oscillatory circuit including a vacuum-tube means I having anode, cathode and control electrodes V and a resonant-circuit means provided by a variable inductor l l and a condenser C. Condenser C is shown in broken-line construction since it may be comprised in whole or in part-of the distributed capacitance of inductor H and the interelectrode capacitance of the anode and control electrodes of tube Ill. The resonant-circuit means an amplifier ll of one or more stages having an input circuit coupled to resistor 33 and having one" or more selector circuits arranged to select predetermined signal components of the output signal of the detector system. A rectifier 42 of conventional construction is coupled to the output circuit of amplifier 4| to rectify the signal component translated therethrough for the pur pose of deriving a control voltage ofnegative polarity. This control voltage is applied to the. input circuit of one or more stages of quenchfrequency amplifier 2| to adjust the amplitude characteristic of the quench voltage so as to control an operating characteristic of the regenerative oscillatory circuit during intervals of wavesignal reception. This control arrangement is generally similar to that which forms the subject matter of application Serial No, 521,932, filed concurrently herewith, in the name of Harold A. Wheeler and assigned to the same assignee as the present invention.

The radio beacon further includes means for supplying to the anode-cathode circuit of tube is coupled to the anode of tube It through a coupling condenser l 2 and has a direct-wire connection to the control electrode thereof; The mid-tap of inductor II is grounded by way of a radio-frequency choke i3 and the cathode of tube III is Iikewisegrounded through a radio-frequency choke l4 and a1 low-impedance bias resistor l5 by-passed for radio-frequency currents by a condenser 'l6,.thereby providing anode-cathode and control electrode-cathode circuits for tube It.

The radio beacon includes means for supplying to the anode-cathode circuit of vacuum tube ID a periodic quench voltage to provide superregeneration for wave-signal reception. This means comprises a quench-frequency oscillation generator 20 which produces a periodic quench voltage of rectangular wave form having a frequency which is low with reference to the'carrler I frequency of the signal to be received and high -with reference 'to the highest modulation frequency thereof to be translated. The output circuit of oscillation generator 20 is coupled to a quench-frequency amplifier 2| of one or more stages and .a cathode-follower type vacuum-tube repeater 22. The cathode load impedance 23 of cathode follower 22 is coupled by means of a coupling condenser 24 and radio-frequency choke 25 to the anode-cathode circuit of tube I0. I

A detector system is coupled to the regenerative oscillatory circuit through a coupling condenser II and constitutes means for deriving irom'the regenerative oscillatory circuit an output signal representing. the modulation of the received signal. The detector system includes a diode detector 30 having as-a load circuit a radio-frequency choke 32 and a resistor 33 which is by-passed for radio-frequency currents by a condenser 34. The output signal of the detector is supplied to a unit 40 which is responsive thererelaxation oscillator which, when keyed, gener-' ates a single positive pulse of unidirectional potential having a substantially rectangular wave form. This pulse as applied to vacuum tube III has a substantially greater magnitude than the quench voltage. The input circuit of generator 50 is coupled to resistor 33 so that the generator is responsive to high-amplitude components of the detected signal output of the regenerative oscillatory circuit, as described more particularly hereinafter.

A single antenna-ground system 60 is utilized for both receiving and transmitting. This system is coupled to the regenerative oscillatory circuit through an inductor 'Bl.

In considering the operation of the described arrangement, it will be assumed initially that no signal are intercepted by antenna-ground system 60. During this no-signal or quiescent operating condition, the quench voltage supplied by generator 20 controls the regenerativeoscillatory circuit to function as a superregenerative receiver having a linear mode'of operation for wave-signal reception. While functioning as a receiver, the

regenerative circuit has predetermined band width and sensitivity characteristics determined largely by the amplitude and frequency characteristics of the applied quench voltage but also determined by such factors as the characteristics of vacuum tube l0 and the resonant circuit coupled thereto. Oscillations are periodically produced in the regenerative circuit under the lnfluence of the applied quench voltage in accordance with the characteristic operation of a superregenerative' circuit. These oscillations which, for the quiescent condition under consideration, are initiated by the noise signals present in the regenerative circuit, have a relatively low amplitude and a frequency which corresponds to the operating frequency of the circuit. This operatto for deriving a control eflect. Unit 40 includes in: freq y during interva s of wave-s a retector 30, producing across resistor 33 a low-.

amplitude periodic signal voltage. This signal has frequency components corresponding to the frequency of the quench voltage and harmonics thereof as well as components corresponding to the noise signals of the regenerative circuit. A portion of this signal, such as the quench-frequency component thereof, is translated through amplifier M and rectifier 42 of unit 40 producing in the output circuit thereof a control voltage of negative polarity having a magnitude determined by the. amplitude of the detected quiescent signal output of the regenerative'circuit. This control voltage is utilized to controlthe operating characteristics of the regenerative circuit during intervals of wave-signal reception, as completely corresponding to that of the applied pulse ofunidescribed inthe above-mentioned copending application. The detected quiescent signal output of the regenerative circuit is also applied'from resistor 33 to the input circuit of generator 50. However, this output signal which has a lowamplitude level i ineffective to trigger generator 50 so that the receiver operation of the regenerative circuit continues uninterrupted.

Let it be assumed now that an aircraft desiring direction-finding information from the radio beacon transmits thereto an interrogating signal comprising a pulse-modulated radio-frequency carriersignal. In general, this interrogating signal will have a high intensity with reference to th noise signals in the regenerative circuit so that the oscillations generated in each quench cycle occurring within the duration .of each received pulse of the interrogating signal have a. relatively high amplitude. During the intervals which intervene between pulses of the interrogating signal, the output signal of detector 30 comprises the low-amplitude quiescent signal described above. The resulting detected output signal, including both the high-amplitude and low-amplitude signal components, is supplied to unit 30 for controlling the operating characteristics of the regenerative circuit. However, the pulse-repetition frequency of the received interrogating signal is usually such that the highamplitude components occur at such a low frequency as to have substantially no effect on the control voltage derived in unit 40. Therefore, this unit responds primarily to the selected component of the quiescent signal output'of the de-* tector to control the operating characteristics of Y the regenerative circuit in the manner indicated above.

This detected outputsignal is also applied to generator- 50 which, in response to the first highamplitude component. derived from each pulse of the received signals, applies tothe anode-cathode circuit of tube [0 a single positive pulse of unidirectional potential. Each applied pulse of unidirectional potential has a predetermined pulse duration, determined by the time constants of I generator 50, and a magnitude which is substandirectional potential. to establish the operating frequency of the regenerative circuit during each interval of wave-signal transmission at a value which is less than that obtaining during intervals-o1 wave-signal reception. The mannerin which this frequency shift is accomplished is to be explained presently. At the trailing edge of each applied pulse of unidirectional potential the quench voltage again becomes effective to control the regenerative oscillatory circuit for an interval of wave-signal reception as described above.

In the usual installation, the time constants of generator 50 are so adjusted that the applied unidirectional potential has a pulse duration substantially equal to that of the received pulses of the interrogating signal. Thus, in response to a received interrogating signal, the radio beacon transmits a" reply signal comprising pulses of radio-frequency energy having the same duration and pulse-repetition frequency as the received interrogating signal. The inquiring aircraft is able to obtain bearing indications from the reply signal.

In considering the operation of the wave-signal transpondor system it has been stated that the operating frequency of the regenerative circuit during intervals of wave-signal reception is determined jointly by the parameters of its resonant circuit and the electron transit time of tube l0. This will be apparent from thefollowing consideration. I

An oscillator essentially comprises an amplifier in which a component of the output voltage is fed back to the input circuit in such a way that the feed-back voltage is in phase with the input voltage required in the input circuit. Oscillations may only be sustained when this phase relation exists. Usually, the output circuit of the amplifier consists of a resonant circuit and thevoltage derived therefrom has a phase-shiftfrequency characteristic as represented by the graph of Fig. 2. Where the eifect of transit time in the amplifierktube may be neglected, the desired phase relation is obtained at the resonant frequency 10 of the resonant circuit so that oscillations may be sustained with the amplifier operating at this frequency value. 0n the other hand, where the circuit is operated in the ultrahigh-frequency range, as in the present case, the transit time of the tube becomes important and may not be neglected. It imparts a lagging phase to the current in the tube and hence to the voltage across the resonant circuit. Therefore, in order to obtain thephase relation required for sustainin oscillations, the operating frequency of the oscillatory circuit adjusts itself to some value, as represented by the ordinate line fr of Fig. 2, such that a compensating leading phase is imparted to the voltage by the resonant circuit. Consequently, sustained oscillations occur at a frequency which is less than the resonant frequency of the resonant circuit. Thus, the operating frequency of the arrangement of Fig. 1, when functioning as a superregenerative receiver, has a predetermined operating frequency fr determined jointly by the parameters of its resonant circuit and the electron transit time of tube Ill. Since the applied quench voltagemayhave a relatively low amplitude for a linear mode of operation of there-e ceiver circuit; the electron transit time of tube It may be a substantial part of the period of oscillation so that this operating frequency fr is Additionally, it is effective considerably less than the resonant frequency of the-resonant circuit provided by inductor H and condenser 0.

During intervals of wave-signal than the quench voltage is effective to reduce the control electrode-anode component of the electron transit time of tube II. This reduction in the electron transit timeproduces a proportionate decrease in the phase-lag effect of tube ll so that a smaller phase-compensating eifect is required to be obtained from the resonant circuit coupled thereto. Consequently, during intervals quency of the regenerative circuit has an increased value as indicated by the ordinate line ft of Fig. 2. 7

The coupling circuits or the described transpondor system which couple the resonant circuit to the control electrode-and cathode of vacuum tube II to provide a control electrode-cathode circuit therefor have an impedance whichis substahtially lower than the impedance of the vacuum tube at frequencies less than that of the quench voltage. This produces a desirable'stability characteristic inasmuch as itobviates the undesirable blocking tendency of certain prior art receivertransmitter arrangements, mentioned above, which include a high-impedance resistor in the control electrode-cathode circuit of the oscillator tube. Furthermore, by applying the quench voltage and the pulse-modulated unidirectional potential to the anode-cathode circuit of tube In a desired shift in the operating frequency of the regenerative oscillatory circuit as between intervals of wave-signal reception and transmission is possible. This result is not ob tained in the prior art arrangements which apply the control potentlals'to the control elec-.

trode-cathode circuit of the oscillator tube since the control electrode-cathode component of the electron transit time has a substantially stabilized value.

It will be apparent from the foregoing descrip tionthat during intervals of wave-signal transmission the quench voltage is present in the anode-cathode circuit of tube Ii. However, during such intervals the applied unidirectional potential effectively overwhelms the quench voltage which is rendered substantially ineffective. If desired, the receiver-transmitter arrangement may be modified, as indicated in Fig. 3, to include means responsive to the unidirectional potential for effectively disabling the supp y circuit of the periodic quench voltage during intervals of waveofTwave-signal transmission, the operating fremodifications as .fall within the true spirit and scope of the invention What is claimed is: 1. A regenerative-type receiver-transmitter arrangeinent for receiving and transmitting modulated carrier frequency wave signals comprising,

a single regenerative oscillatory circuit including resonant-circuit means and vacuum-tube means coupled thereto having an anode-cathode'cir-' cult, means for supplying to said anode-cathode circuit a periodic quench voltage to provide superregeneration for wave-signal reception and to determine the electron transit time of said vacuumtube means sothat said regenerative oscillatory circuit has a predetermined operating frequency during intervals of wave-signal reception determined jointly by the parameters of said resonantcircuit means and said electron transit time, said signal to be received and high with reference to the highest modulation frequency thereof to be -translated, means for deriving from said regenerfative oscillatorycircuit an output signal representing the modulation of said received signal, and means forgsupplying to said anode-cathode :ircuit a modulated potential for controlling said regenerative oscillatory circuit to transmit a modulated carrier-frequency signal and having a lsubstantially greater magnitude than said quench voltage so as to efiect a predetermined modification of saidelectron transit time of said vacuumtube means, thereby to produce a related modincation of said operating frequency of said regenerative oscillatory circuit during intervals of waveesignal transmission.

2.- n regenerative-type receiver-transmitterv arrangement for receiving and transmitting modulated carrier-frequency wave signals comprising,

a single regenerative oscillatory circuit including resonant-circuit means and vacuum-tube means coupled thereto having an anode-cathode circuit,

means for supplying to said anode-cathode circuit signal transmission. 'Fig'. 3 represents that por tion of the Fig. 1 arrangement included within broken-line rectangle II and shows the cathode follower 22 is driven positive to block the cathode follower and disable the supply circuit for the quench voltage.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modiflcations may be made therein without departing from the invention, and it is, therefore, aimed inthe appended claims to cover all such changes and a periodic quench voltage to provide super-regeneration for wave-signal reception and to determine the electron transit time ofsaid vacuumtube means so that said regenerative oscillatory circuit has a predetermined operating frequency during intervals of wave-signal receptiondetermined jointly by the parameters of said resonantcircuit means and said electron transit time, said quench voltagehaving a frequency which is low with reference to the carrier frequency of the signal to be received and high with reference to the highest modulation frequency thereof to be transof said vacuum-tube 'means a predetermined amount, thereby to increase said operating fre 1 quency of said regenerative oscillatory circuit to a predetermined value during intervals of wavesignal transmission.

3. A regenerative-type receiver-transmitter arrangement for receiving and transmitting modulated carrier-frequency wave signals comprising, a single regenerative oscillatory, circuit including vacuum-tube means having an anode-cathode circuit, means for supplying to said anode-oathsuperregeneration for wave-signal reception, said quench voltage having a frequency which is low with reference to the carrier frequency of the signal to be received and high with reference to the highest modulation frequency thereof to be translated, means for deriving from said regenerative oscillatory circuit an output signal representing the modulation of said. received signal,-

means for supplying to said anode-cathode circuit a modulated potential for controlling said regenerative oscillatory circuit to transmit a modulated carrier-frequency signal, and means responsive to one of said periodic quench voltage and said modulated potential for effectively disabling said means for supplying the other of said quench voltage and said modulated potential to said anode-cathode circuit.

4. A regenerative-type receiver-transmitter arrangement for receiving and transmitting modulated carrier-frequency wave signals comprising,

a single regenerative oscillatory circuit including vacuum-tube means having an anode-cathode circuit, means for supplying to sai anode-cathode circuit a periodic quench voltage to provide a signal to be received and high with reference to the highest modulation frequency thereof to be translated, means for deriving from said regensuperregeneration for wave-signal reception, said quench voltage having a frequency which is low with reference to the carrier frequency of the signal to be received and high with reference to the highest modulation frequency thereof to be translated, means for deriving from said regenerative oscillatory circuit an output signal representing the modulation of said received signal, means for supplying to said anode-cathode circuit a modulated potential for controlling said regenerative oscillatory circuit to transmit a modulated carrier-frequency signal, and means responsive to said modulated potential for effectively disabling said -means for supplying said periodic quench voltage during intervals of wavesignal transmission.

5. A regeneratiye-type receiver-transmitter arrangement for receiving and transmitting modulated carrier-frequency wave signals comprising, a single regenerative oscillatory circuit including vacuum-tube means having an anode-cathode circuit, means including a vacuum-tube repeater for supplying to said anode-cathode circuit a periodic quench voltage to provide superregeneration for wave-signal reception, said quench voltage having a frequency which is low with refer-.

ence to the carrier frequency of the signal to be received and high with reference to the highest modulation frequency thereof to be translated, means for deriving from said regenerative oscillatory circuit an output signal representing the modulation of said received signal, and means responsive to said output signal for supplying to said anode-cathode circuit a modulated potential for controlling said regenerative oscillatory circuit to transmit a modulated carrier-frequency signal and for blocking said repeater to disable said means for supplying said periodic quench voltage during intervals of wave-signal transmission.

6. A regenerative-type receiver-transmitter arrangement for receiving and transmitting modulated carrier-frequency wave signals comprising, a single regenerative oscillatory circuit including vacuum-tube means having an anode-cathode -circuit, means for supplying to said anode-cathode circuit a periodic quench voltage to provide superregeneration for wave-signal reception, said quench voltage having a frequency which is low with reference to the carrier frequency of the erative oscillatory circuit an output signal representing the modulation of said received signal, and means responsive to said output signal for pp y g to said anode-cathode circuit a modulated potential for controlling said regenerative oscillatory circuit to transmit a modulated carrier-frequency signal and for disabling said means for supplying said periodic quench voltage during intervals of wave-signaI transmission.

7. A regenerative-type wave-signal transpondorsystem for transmitting a pulse-modulated reply signal in response to a received pulsemodulated interrogating signal comprising, a single regenerative oscillatory circuit including vacuum-tube means having an anode-cathode circuit, means for supplying to said anode-cathode circuit a periodic quench voltage to provide superregeneration for wave-signal reception, said quench voltage having a frequency which is low with reference to the carrier frequency of said received signal and high with reference to the highest modulation frequency thereof to be translated, means for deriving from said regenerative oscillatory circuit an output signal including high-amplitude components determined by the pulse modulation of said received signal, and means responsive to said high-amplitude component for supplying to said anode-cathode circuit apulse-modulated potential for controlling said regenerative oscillatory circuit to transmit a pulse-modulated reply signal.

8. A regenerative-type receiver-transmitter arrangement for receiving and transmitting modulated carrier-frequency wave signals comprising, a single regenerative oscillatory circuit including vacuum-tube means having an anode-cathode circuit, an oscillation generator for supplying a periodic quench voltage having a frequency which is low with reference to the carrier frequency of the signal to'be received and high with reference to the highest modulation component thereof to be translated, a vacuum-tube repeater connected in cascade with said oscillation generator for applying said quench voltage to said anode-cathode circuit to provide superregeneration for wavesignal reception, means for deriving from said regenerative oscillatory circuit an output signal representing the modulation of said received signal, and means for supplying to said anodecathodecircuit a modulated potential for controlling said regenerative oscillator circuit to transmit a modulated carrier-frequency signal.

' HAROLD A. WHEELER.

REFERENCES CITED The following references are of record in the vfile of this patent:

UNITED STATES PATENTS British -4 Apr. 5, 1937 

